This invention relates to an improvement of a multiple control valve system which comprises a multiple control valve and valve means attached thereto.
Various types or forms of multiple control valves have been widely used and known in the art of this field, and a typical example of these valves will be described hereunder in conjunction with FIG. 1. FIG. 1 shows a multiple control valve 11 having a plurality of spools for changing flow direction of an oil passing through the multiple control valve in which a valve body 12 is provided with an inlet chamber 13 into which a pressurized oil is supplied from an external oil source through a pump 14. The pressurized oil is discharged, under an unloaded condition, into a drain tank 19 through a by-pass passage 18 formed at the central portions of the valve body 12 to be opened by spools 15 and 17 when the spools 15 and 17 occupy their neutral positions as shown in FIG. 1. The pressurized oil is also supplied to the spools 15 and 17 in communication with side passages 20 and 21 connected to and extending from the inlet chamber 13.
When a spool 16 is moved rightwardly as viewed in FIG. 1, the by-pass passage 18 is closed by an enlarged central portion and outer surface of the spool 16 and the side passage 20 comes to communicate with a hole 22 provided for the spool 16, whereby the pressurized oil is guided to one hydraulic chamber located on one side of an actuator, not shown, which hydraulically operates through an axial hole, not shown, of the spool 16, a hole 23, and a cylinder port 24. A pressurized oil in the other hydraulic chamber on the other side of the actuator flows into the tank 19 through a cylinder port 25, holes 26, 27, and a return passage 28.
In a case where a multiple control valve such as shown in FIG. 1 is incorporated in a civil machine, for example a bulldozer, the spools 15 and 17 of the control valve 11 are operatively connected to a travelling motor and actuators of a bucket and a boom, respectively. A recent civil machine is often provided with a hydraulic breaker as an attachment member in addition to the travelling motor and the actuators of the bucket and the boom.
One example of such a multiple control valve is shown in FIG. 2 in which like reference numerals are applied to elements corresponding to those shown in FIG. 1 or a capital letter "A" is added thereto, and the multiple control valve provided with an additional valve is referred to as a multiple control valve system hereunder.
A multiple control valve 11A shown in FIG. 2 is different from that 11 shown in FIG. 1 in that an inlet chamber 13A of a valve body 12A does not communicate with side passages 20A and 21A, which are connected to a pump 14 through conduits 31 and 33. The valve body 35 of a valve 34 (called an attachment valve 34 hereinbelow) attached to the valve 11A is provided with an inlet chamber 36 which is connected to a drain tank 19 through the pump 14. When the spool 37 of the attachment valve 34 occupies its neutral position as shown in FIG. 2, pressurized oil supplied to the inlet chamber 36 flows into the inlet chamber 13A of the multiple control valve 11A through a by-pass passage 38, a central portion of the spool 37, and a pipe 39 which is communicated with the inlet chamber 13A, and then the pressurized oil is discharged into the tank 19 where the spools 15 and 17 occupy their neutral positions.
In the meantime, when the spool 16 of the valve 11A is moved rightwardly as viewed in FIG. 2, as described in connection with FIG. 1, the by-pass passage 18 is closed and the pressurized oil entered into the passage 20A is fed into one hydraulic chamber located on one side of an external actuator, not shown, which hydraulically operates, through holes 22, 23 and the cylinder port 24. The pressurized oil in the other hydraulic chamber on the other side of the actuator is discharged into the tank 19 through the cylinder port 25, holes 26, 27, and the passage 28. When the spool 37 of the attachment valve 34 is moved rightwardly, the pressurized oil in the inlet chamber 36 is fed to one hydraulic chamber located on one side of an actuator, not shown, which operates hydraulically, through a side passage 40, holes 41, 42, 43, and a cylinder port 44 and the pressurized oil in the other hydraulic chamber on the other side of the actuator is discharged into the tank 19 through a cylinder port 45, holes 46, 47, 48, and a return passage 49.
With the multiple control valve system shown in FIG. 2, the valve body 12A of the multiple control valve 12A is different from the valve body 12 of the valve 11 in their constructions because the conduits 31 and 32 are connected to the valve body 12A, so that it is impossible to apply a usual multiple control valve as shown in FIG. 1 as it is to a multiple control valve system as shown in FIG. 2 and it is obliged to manufacture independently the valve body 12A without utilizing the valve body 12. This inconvenience results in the increase in the manufacturing cost as well as manufacturing steps.